The T. Webber U.S. Pat. No. 4,663,513 discloses a system for monitoring a laser process in which a laser source is employed for delivering energy to a workpiece along a process path while producing plasma at a beam delivery point along the path. An infrared detector receives infrared radiation from a point behind and in close proximity to the location of the beam delivery point. The radiation detector provides an analog temperature signal having a value which varies over time with changes in the intensity of the received infrared radiation. The analog temperature signal is compared against a window range of acceptable temperatures including a fixed upper limit and a fixed lower limit. If the temperature signal is not within the window range, then the output of the laser process, such as a welding process, is rejected.
It is to be particularly noted that the system described in the aforesaid patent provides either a process rejection or acceptance depending upon whether the temperature signal has a value which is within the window range or which is outside of the window range. Consequently, this is a pass-fail test. No teaching is presented for determining relative quality of the laser process. There is no suggestion that a plurality of samples be taken of the temperature signal with each of the samples being compared with a plurality of different temperature limits, the results of such comparisons being used to calculate a quality factor.
Still further, the aforesaid patent provides a fixed upper limit. This does not allow for a laser process having ranges of different, but normal, temperature values. For example, in a laser weld process, there is a turn-on overshoot condition which has an increased temperature. There may also be a weld overlap region on a workpiece which may produce an increased temperature during the weld process as the laser beam passes over a previously welded area.
Moreover, the aforesaid patent does not provide for archival storage of information so that the data obtained from a laser process analysis may be reviewed at a later point in time.
Additionally, the aforesaid patent does not provide for differentiating between normal weld sparking and detrimental splatter conditions when evaluating a laser weld process.
The present invention is directed toward improvements over the process and apparatus of the aforesaid patent to satisfy the foregoing shortcomings.